The present invention generally relates to a communications interface, and in particular relates to a communications interface between an appliance and a power line carrier communication system.
The typical home, office building, or commercial establishment contains several appliances, including refrigerators, microwave ovens, ovens, stoves, heating systems, cooling systems, and the like. Modem appliances are much more sophisticated than their early counterparts, and often include microcontrollers or microprocessors that allow the appliance to be programmed, reprogrammed, and provide diagnostic information, as examples.
The Internet has given rise to worldwide connectivity for many types of devices. Appliances, however, only have traditional standalone capability. Three primary communication technologies may be used to provide appliance connectivity: hard wiring, power line carrier (PLC), and wireless.
Hard wiring (including for example RS-232, RS-485, Ethernet, USB, HomePNA, and industrial twisted pair networks) offers superior performance capability (when measured in terms of speed, noise immunity, and the like) at an effective cost. However, a drawback is that additional wiring is required to a home or business. Hard wiring thus poses the significant problem of retrofitting networked appliances into existing homes and businesses and increases cost for new structures.
PLC uses a 120V or 240V AC power line as a carrier for networking data by modulating the networking data on a high frequency carrier. The high frequency carrier is usually between 100–400 kHz to keep it below the range of FCC regulation. Although older technologies, such as X10, have achieved some market acceptance in lighting applications, they are generally deemed too slow and unreliable for major appliance networking needs. However, newer PLC technologies, such as CEBus and LonWorks, are now commercially available and provide improved data rates and noise immunity at reasonable cost.
Wireless technologies (such as IEEE 802.11, Bluetooth, HomeRF, and the like) solve the problem of additional wiring by modulating data onto a radio frequency carrier (e.g., at 2.4 GHz) that is broadcast via antenna to desired recipients. Wireless approaches may offer higher bandwidth than PLC technologies currently available, but they do so at a higher cost. Furthermore, since most major appliances are packaged in a sheet steel enclosure (which makes an effective RF shield), antenna placement may be difficult. Cost effective wireless technologies are also subject to distance limitations, potential interference, and poor reception zones that can often render their use in the home with large, immobile appliances impossible.
Therefore, even though PLC technologies are still emerging, they may offer the best balance of cost and performance in appliance networking. As such, a need exists to develop an appliance communication controller that interfaces appliances to an AC power line for communicating across the power line.